May I know the size of the PF Condenser you are using? What I have in the car right now is a 14"x22" PF Condenser. It cooled the car pretty well in the beginning. I was getting <40F on a hot 90F+ day with R134A. The compressor developed a knock recently which i think was caused by the higher pressure but i cant confirm it as i did not check with the gauges yet. I dont know if a bigger PF condenser will help with lowering the pressure. Im plannng to switch to R12.

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'85 300D Cal 280,000 miles
'14 GLK 350 60000 miles